Interpretive Summary: Exposing rats to high energy radiation particles has been shown to disrupt systems in the brain and the behaviors these systems mediate in a similar way as seen during aging. In one part of the brain that plays a role in learning and memory, the hippocampus, production of new brain cells is affected by both aging and irradiation. In addition, the development and migration of these newly generated cells has been found to be affected in aging. This present study was designed to investigate the effects of high energy iron particles on the production and development/migration of new cells produced as wel as affects thier development and migration. Given that similar results have been found in aged animals,it is suggested that irradiation with heavy iron particles is a valid model of aging. Also, given that these same particles are present in cosmic rays, these results provide a cautionary word for those astronauts traveling on long-term mission to space.

Technical Abstract:
Exposure to particles of high energy and charge are disruptive to neuronal systems and the motor and cognitive behaviors mediated by them ina similar fashion to that seeen during aging. In the hippocampus, the proliferation of new neurons can be modulated both by aging and irradiation with ionizing particles. Likewise, the migration and maturation of newly formed cells in this region is also altered by the aging process. The present study was designed to investigate the effects of 2.5 Gy of 1GeV/n 56Fe particles on hippocampal neurogenesis and PSANCAM the expression, immunohistochemicaly, using the proliferation marker 5-bromodeoxyuridine (BrdU), in the dentate gyrus of rats exposed to whole=body irradiation and sacrificed 28 days after the last BrdU injection. Our results illustrate that exposure to 56Fe particles decreased the number of BrdU-positive cells and PSA-NCAM expression in this region. Given that aged animals show similar neurogenesis and PSA-NCAM expression patterns, we suggest that irradiation with 56Fe particles is a valid model of aging. Furthermore, given that 56Fe particles are present in cosmic rays, our results provide a cautionary word for those astronauts traveling on long-term missions to space.